1. Field of the Invention
This invention is directed to an apparatus and method that generates radiant energy for use in processing a substrate and/or integrated devices or circuits formed thereon. For example, the apparatus and method can be used to supply radiant energy to anneal and/or activate dopants of source, drain or gate regions of integrated devices or circuits, to form silicide regions in integrated devices or circuits to lower contact resistances of metal wiring coupled thereto, or to trigger a chemical reaction to either form or remove substances from a substrate. The invented apparatus and method can also be used to generate, pattern, and direct radiant energy to a substrate for selective treatment thereof.
2. Description of the Related Art
Various devices for laser treatment of semiconductor substrates have been known and used in the integrated circuit fabrication industry. Laser annealing is preferably done in a single cycle that brings the temperature of the material to be annealed up to the annealing temperature and back down in a single cycle. If a pulsed laser is used, this requires enough energy per pulse to bring the entire chip or circuit up to the annealing temperature. Because the required field size can exceed four (4) centimeters-squared (cm2) and the required dose can exceed one (1.0) Joules/cm2, a relatively large, expensive laser is required. It is also difficult to achieve good dose uniformity over a relatively large area in a single pulse because the narrow spectral range of most lasers produces a speckled pattern due to interference effects.
An alternative approach is to use a continuous laser, which illuminates a relatively narrow line spanning the width of a chip or group of chips on a substrate, and to continuously scan the illuminated line image over the substrate. Although the relative complexity and expense of a laser apparatus using this approach can be greatly reduced relative to single-pulse laser systems, there is still considerable room for improvement of the image intensity and quality, as well as for reduction in the complexity and cost of such line-scanning apparatuses. It would be desirable to provide a line-scanning apparatus that generates a relatively high-intensity line image for treating integrated devices formed on a semiconductor substrate. It would further be beneficial to provide an apparatus with a configuration that is greatly simplified, and less expensive, as compared to previous devices and that provides superior uniformity of radiant energy along the length of the line image relative to previous devices and techniques.
It is an object of the invention to provide an apparatus that generates relatively intense radiant energy for processing a substrate.
It is an object of the invention to provide an apparatus that can be used to expose a relatively large rectangular area or strip across a substrate.
It is an object of the invention to provide an apparatus that can uniformly irradiate and process a substrate with radiant energy.
It is an object of the invention to provide an apparatus for processing a substrate with radiant energy that is relatively simple in construction and is readily manufactured.
The invented apparatus overcomes the above-stated disadvantages, and attains the above-stated objects and advantages. The invented apparatus includes at least one line source with one or more laser diodes. The laser diodes can be components of one or more laser diode array bars. Each laser diode array includes a plurality of laser diodes arranged at intervals along a linear emission face of the array. The source can be used to irradiate a relatively narrow line or strip image on a substrate. The substrate can be a semiconductor wafer, for example. Each laser diode array includes a plurality of laser diodes arranged at intervals along a linear emission face of the array. The apparatus also includes an anamorphic relay. The anamorphic relay receives and directs radiant energy from the line source to the substrate to form the line image thereon. The anamorphic relay can be configured so that each point along the length of the image generated by such relay is illuminated by radiant energy from more than one, and optionally many or all, laser diodes of the apparatus. Accordingly, the intensity of the line image at each point thereof is relatively uniform even though the radiant energy generated by each laser diode may vary, because the intensity at each such point in the image is the average of that radiant energy generated by more than one laser diode. The line image is therefore relatively invariant to fluctuations in the radiant energy generated by any one laser diode.
The apparatus can further include a controller, a power supply, a stage, a stage controller, an input unit, a display unit, and a radiant energy detector. A user can manipulate the input unit to generate one or more signals indicative of predetermined processing parameters including dose of radiant energy, intensity of radiant energy, scan speed, and/or number of scans to process the substrate. The input unit is coupled to supply the parameter signals to the controller. The controller can be coupled to receive a start signal generated by a user""s manipulation of the input unit. Alternatively, the start signal and operating mode can be generated externally from the apparatus, for example, by a master controller of an assembly of machines for a production line in which the apparatus is a part. In response to the start signal that initiates the apparatus"" operation mode, the controller generates and supplies an intensity control signal to the power supply, which generates a regulated electric current based thereon. The line source receives the current, and generates radiant energy based on such current. From the line source, the radiant energy travels to the substrate via the anamorphic relay to form the line image thereon. Also in response to the start signal, the controller generates a scan control signal based on the parameter signals indicating the predetermined dose and scan speed, optionally also the number of scans to be performed to process the substrate. The controller is coupled to supply the scan control signals to the stage controller. Based on the scan control signal, the stage controller generates a scan signal. The stage controller is coupled to supply the scan signal to the stage on which the substrate is situated, to position the substrate relative to the anamorphic relay and line source. The detector is used in the apparatus"" preparation mode. The detector is positioned on the stage, and receives radiant energy generated by the line source. The detector generates a detector signal indicative of the radiant energy received by the substrate. The detector is coupled to the controller that integrates the detector signal to produce a signal indicative of the radiant energy dose received by the detector. Generally, the detector is used in the apparatus"" calibration mode to adjust the line image intensity and/or the scan speed to deliver a predetermined dose of radiant energy to the substrate.
A method in accordance with the invention includes generating radiant energy with a plurality of laser diodes, and anamorphically focusing the radiant energy to a substrate to form a line image to process the substrate. The invented method achieves similar advantages as previously described with respect to the apparatus.
These together with other features and advantages, which will become subsequently apparent, reside in the details of the invented apparatus and method as more fully hereinafter described and claimed, reference being made to the accompanying drawings, forming a part hereof wherein like numerals refer to like parts throughout the several views.